There are a number of known methods for isolating DNA, RNA and proteins from biological material. For example, it is known that an ultra-centrifugation of a sample homogenate in a guanidine-cesium chloride solution may be employed. The sample may be homogenized in 4 molar (M) guanidine thiocyanate and then over-layered on a cesium chloride (CsCl) solution and centrifuged at greater than 100,000 g for a long period of time. Following centrifugation, DNA, RNA and proteins may be separated and purified.
U.S. Pat. No. 5,346,994 teaches a method of isolating DNA, RNA and proteins based on liquid-phase separation using phenol and guanidine thiocyanate. A biological sample is homogenized in an aqueous solution of phenol and guanidine thiocyanate and the homogenate thereafter is mixed with chloroform. Following centrifugation, the homogenate separates into an organic phase, an interphase and an aqueous phase. Proteins are sequestrated into the organic phase, DNA into the interphase and RNA into the aqueous phase.
U.S. Pat. No. 5,945,515 discloses a product and process for isolating DNA, RNA and proteins with a solution that includes effective amounts of chaotropic agent, buffer, reducing agent, and water, with or without organic solvents.
Other conventional protocols generally entail use of phenol or an organic solvent mixture containing phenol and chloroform to extract proteins and lipids from a conventional lysate solution. The phenol/chloroform extraction step is generally followed by precipitation of the nucleic acid material remaining in the extracted aqueous phase by adding ethanol to that aqueous phase. The precipitate is typically removed from the solution by centrifugation, and the resulting pellet of precipitate is allowed to dry before being re-suspended in water or a buffer solution for further processing or analysis.